When should you use a junction box?

A small metal or plastic junction box can be part of an electrical channel or thermoplastic cable system (TPS) in a building. If it is designed to mount the surface, it is mainly used on roofs, low floors or hidden behind an access panel, especially in domestic or commercial buildings.A junction box may be a part of an electrical conduit in a building. It's used mostly in ceilings, under floors or hidden behind an access panel in domestic or commercial buildings if it's designed for surface mounting.